1. Field of the Invention
This invention relates to screen inserts for doors and windows and more particularly to rigid screen inserts which sandwich the screen material between opposing frame members.
2. Prior Art
The use of screen material in doors and windows has been popular for decades for providing air flow into a room while preventing entry of insects and wind born debris. In window applications, screen material may be easily mounted on a frame which is positioned in a window opening and usually does not require special mounting structure to maintain its proper placement.
Screen inserts which are positioned in doors, however, are subject to more stringent conditions. For example, it is not uncommon for persons exiting a room to push on the screen insert for the purpose of opening the door as they exit. Most screen inserts are not adapted with structure to prevent the force applied to the screen material from displacing the screen from its point of attachment. Where young children are involved, the applied force to the screen material may be quite severe and may quickly lead to full detachment of the screen material.
The most common means for mounting screen material into an opening of a screen insert frame involves a peripheral channel formed in the frame which is sized to receive a smaller diameter rubber insert which captures the screen material within the channel when the insert is pressed therein. This offered the advantage of enabling simple repair following displacement by merely restretching the screen across the opening of the insert and repositioning the components to their original configuration.
Numerous improvements have been attempted to make screen attachments more permanent and stable. U.S. Pat. Nos. 1,212,676; 3,086,628 and 3,696,857 disclose a series of improvements which involve capturing the screen at a single gripping edge. In these instances, the screen material is stretched to a taught configuration and the gripping edge is applied against the frame, with the screen sandwiched therebetween. The disadvantages of this method of attachment include tearing of the screen material under nominal force and loss of tension in the screen stretched across the insert opening. This arises in part because of the localized stress which is totally focused along the gripping edge.
A second method for securing the screen material within the insert opening is represented by U.S. Pat. Nos. 2,436,277; 3,220,469; and 4,084,360. These three patents are representative of techniques which involve sandwiching the screen material between opposing plates which are compressed to grip the screen material therebetween. Essentially, opposing flat surfaces frictionally grip the screen material as they are forced toward each other. Several of these patents suggest the utility of having an arcuate configuration in which an insert portion extends into the arcuate cavity such that linear force applied along the screen material is resisted primarily at the juncture of a plane containing the screen material and a deviation of this screen as it wraps through the arcuate cavity, held by the inserted structure which is compressed against the screen. This prior art shows a number of variations of quick release, clip-on structure which facilitates removal of the opposing frame members such that the sandwiched screen can be repositioned in a taut configuration, with the opposing frame members being reconnected to grip the screen securely.
Although these various improvements have enhanced the ability of the screen material to resist strong forces applied, even these configurations will release or permit the screen to loosen when subjected to sever forces. In fact, if steel screen material is applied, its ability to survive extreme impacts results in the peripheral edges of the screen being pulled free from the support structure. What is needed is a different support system which has sufficient strength to resist release of the screen material from its sandwiched position, even with sever blows.